Posted
by
samzenpus
on Wednesday January 23, 2013 @11:04PM
from the keeping-it-cool dept.

MatthewVD writes "Infrared cameras on satellites and night vision goggles could soon use lasers to cool their components. According to the study published in Nature, researchers in Singapore were able to cool the semiconductor cadmium sulfide from 62 degrees fahrenheit to -9 degrees by focusing a green laser on it and making it fluoresce and lose energy as light. Since they require neither gas nor moving parts, they can be more compact, free from vibration and not prone to mechanical failure."

I've known more than a few USians who left and went to Singapore because the funding situation is a lot less hassle-- no more proposals to underfunded agencies with low hit rates for small pots of money. Singapore sets them up with a nice lab and stable funding so they can do the things they went into science for in the first place. It doesn't sound bad, but I wouldn't really want to live in Singapore.

If you want to turn 40 watts of heat into blue light, I'm figuring that's something like 5000 lumens you're creating according to the luminosity function. That's a conference room projector worth of light. Then you have to figure the laser power required to get that much heat out, which according to the article's 2 percent efficiency estimate would be...a lot. I don't know how "cooling efficiency" is defined.
Ideally you'd move the emission to infrared, but that would be disastrous for your night vision

Rapid pulsing lasers (femtolasers) can drastically increase the wattage without actually increasing the number of joules drawn. Without having read the article (this is/. after all), it seems to me that using a pulsed laser would actually be better for this kind of application, because the medium being cooled needs time to actually let off the photons being generated.

That being said, yes, I imagine that active cooling methods are probably significantly more energy efficient, at least for the moment. A pelt

Been saying lasers are cool for ages, but do they listen to me? Nooo...

So I'm out with the astronomy club with all our cool glass and tubes and stuff and have people looking at Jupiter, Saturn, Mars, M-13, fun stuff like that there. Someone asks, "Which star is Sirius?" I pull out my laser pointer and show them. Little kid says, "Whoa! That's COOL! Mom! Buy me one!"

I tell the mother, "No, do not buy him one. Laser is not toy. Can blind himself or a friend with it. Under no circumstances should you buy him a laser. Buy him a UV flashlight to look at centipedes or something."

These pointer lasers are controlled items in many places because, aside from the obvious general hazard, morons deliberately point them at aircraft cockpits. Only occasionally do the fools get identified [abc.net.au] but it warms the cockles of my heart when they do: I am an amateur astronomer and have also been involved in the airborne end of this stupidity.

Agreed, having worked with a lab that certifies products sold in the US (21 cfr) and internationally (60825-1 and -2), lasers have gotten more powerful and compact than most folks realize. Class 4 lasers are easily integrated into the handheld green pointers that most of us have seen. What isnt realized is that the 150mw pointers that will blind you like a thief in the night. I have posted blue 445nm and green 532nm lasers to youtube that I have made burning through objects in close proximity, remember t

That shouldn't be an obstacle, as current refrigeration technology doesn't directly cool the air in your fridge/home/office either. It would be possible to cool some object using the laser then use the low temperature of the now cold object to cool the surrounding air. However as long as the efficiency is indeed 1.2-2% as mentioned in an adjacent comment this is no replacement for current A/C tech.

Possibly not too efficient. But, this process has a huge advantage over current methods that is completely ignored by the article and many slashdotters so far: it would work in a vacuum. And when you're the only viable method in town for a certain niche, efficiency doesnt matter so much.

The cool in Doppler cooling comes from absorbing the photon which changes the kinetic energy of the atom, then fluorescence that does not contribute back to the heating. Here, it is dependent on the semiconductor band structure, and involves absorbing the photon, then a release of another photon and a phonon to cancel out lattice vibrations.

The primary purpose of Night Vision goggles is to see clearly in the dark in those times where you can't/won't use a torch. So, in times where you may not want to be seen yourself. How is it helpful to have the goggles shine with green laser light to cool them off in this situation?

Presumably the system would be completely self contained. Neither the laser nor the fluorescing being visible. Maybe we can think of the fluorescing as a mechanism to conduct heat from the electronic components to the case of the NVG. Of course that would heat up the NVG case but perhaps it is not emitting in the iR anymore than the person's face underneath it. More info is needed.

Presumably the system would be completely self contained. Neither the laser nor the fluorescing being visible. Maybe we can think of the fluorescing as a mechanism to conduct heat from the electronic components to the case of the NVG. Of course that would heat up the NVG case but perhaps it is not emitting in the iR anymore than the person's face underneath it. More info is needed.

I've seen multiple posts like this one, and they all seem to be missing a huge point (maybe I'm getting trolled?... or maybe I'm completely wrong).

From the article (sorry, I read it):"...starting from 290 kelvin. We use a pump laser with a wavelength of 514 nanometres, and obtain an estimated cooling efficiency of about 1.3 per cent and an estimated cooling power of 180 microwatts."

Where the hell is all the heat going if you stick this thing inside some goggles with the direct purpose of cooling something inside said goggles? That question has nothing to do with the above quote... it's there to drive it home - look at how inefficient this process is!?! I'm sure it's extremely useful and interesting for a great many cases, but I don't see (pun) how this is good for night vision goggles.

... How is it helpful to have the goggles shine with green laser light to cool them off in this situation?

Presumably the system would be completely self contained. Neither the laser nor the fluorescing being visible. Maybe we can think of the fluorescing as a mechanism to conduct heat from the electronic components to the case of the NVG. Of course that would heat up the NVG case but perhaps it is not emitting in the iR anymore than the person's face underneath it. More info is needed.

I've seen multiple posts like this one, and they all seem to be missing a huge point (maybe I'm getting trolled?... look at how inefficient this process is!?! I'm sure it's extremely useful and interesting for a great many cases, but I don't see (pun) how this is good for night vision goggles.

I'm not arguing that it would work or even be practical. There must be easier ways to conduct heat, methods that don't add to battery usage. I'm just pointing out that the laser and the fluorescence are internal to the unit, and that only key electronic components need to be cooled not the entire unit.:-)

There's no law of preservation of heat, only preservation of energy. Presumably, part of the heat energy is transformed into light, and part of it is stored into the reactant products. Think of those portable heat packs. "If the pack itself is at room temperature, where does the heat come from?" Also, heat != temperature.

It is a "new" way to move heat. In night vision goggles, it could move heat from the sensor to the casing, as only the sensor (and perhaps the optics) must be cold. However, I would imagine a Peltier element being more efficient, and that this mostly makes sense where a) You have no heat sink (mostly in space, I guess) or b) The cooling devices is not in direct contact with what is being cooled (the technique is already used in this way to cool gasses for making Bose Einstein condensates, where the thing be

Things in space and really cold stuff makes perfect sense. Both articles even point to that for the most part.The night vision thing is only mentioned in the dumbed down txchnologist piece, and only once, and via a small quote from someone that wasn't even involved in the project:

“The big potential users of this cooling technology are night-vision goggles, and infrared cameras on satellites, where weight is very important and you would not want the motors and pumps and vibrations that come with regular coolers if you can,” says Richard Epstein, a University of New Mexico physicist and CEO at technology startup ThermoDynamic Films, who did not take part in this research.

I'd love to know the rest of the context for that comment, because it seems absolutely crazy to me that night-vision goggles and infrared cameras on satellites are _THE_ big potential users of one given cooling technology... those

It's only the sensor that needs to be cooled below ambient, other parts can use traditional methods. So, you make the back side of the sensor flouresce, capture that light in a chamber where it is converted back to heat, then dissipate that heat through regular air cooled heatsinks.

In the end it's just shifting the heat whilst working against a thermal gradient - same as a refridgerative system, but without moving parts.

The scientists used SI units all the way through in their paper (Kelvin for temperature), and they would have been laughed out of court and certainly not published in Nature if they'd done otherwise.

Why does Slashdot even accept a submission in Fahrenheit when the subject is science? Most nerds understand SI units, and most of the planet is metric. How about trying to be a bit educational for the few that don't? Quote both if you're trying to be helpful, with the SI units as primary for science reporting and imperial equivalents only in brackets.

Depends on the desired temperature, where you are in space, and where you have to move the heat from and to, and how much heat you have to move. Peltier coolers are indeed used in space, along with many other cooling technologies. All active coolers in space get tied to passive radiators to dump the waste heat.

Handy for things like uranium isotope separation, and also for creating things like Bosenovas. The problem is, that the process is very sensitive to the frequency of the laser. If these guys have found a way to reliably, inexpensively create the right frequency of light to cool anything...then that substance can act as a heat sink to cool other substance. This could open a whole exciting new era of science and technology. But I won't hold my breathe, the proof is in the pudding, etc.

We have our refrigerator laser, now all we need is a stasis generator, to "control the flow of tune and space through the body of the Sunship, so that the violent tossing of the chromosphere would seem a gentle rocking to those inside." And I'm sure we'll have that any day now.

That must be why the mother ship has all those lights. Cooling lasers.
The overlords see in the heat spectrum (or not at all) and so never expected us to detect them.
Blaart: It's like the huuuman is looking right at ussss.
Pleaotard: Not possible, Overlord Blaartumus. We have the cooling lasers working overtime.

Well, put some of that semiconductor underneath the base plate, aim a 800W laser at it contained inside the device - depending on the speed the material loses heat at, it might be possible to make a "microwave freezer" that freezes (or at least cools) things in seconds.

Probably pie-in-the-sky because of some physical limit (i.e. it might take hours to cool no matter how much power you aim at it), but the "microwave freezer" has been an April Fool "hoax" on at least one BBC science programme (Tomorrow's Worl

1.2% efficient isn't bad for the first go at getting this effect with semiconductors though.

Hell, I bet early solar panels weren't even that efficient, and they are all over the world now.

You would need to get to about 50% efficiency to make them useful, though, but with no-moving parts and all the other advantages, probably even less than that would make them have practical application.